The proposed research seeks to complete a system for automated threshold audiometry using the middle components (8-90msec) of the averaged electroencephalic response (AER) as the response index. The initial project period helped to establish the parameters and procedures for stimulus presentation, response recording, response formatting, response identification or categorization, and threshold quantification. Computer programs for stimulus presentation, and for off-line response categorization and threshold quantification have been incorporated into a system for objective measures of tonal threshold. The system has already been tested on young, normal-hearing adult, normal neonates, and some hearing-impaired subjects. In the current project period, the system will be validated on larger samples of hearing-impaired subjects, and on subjects with CNS lesions affecting auditory function. Normal infants from 1 week through 9 months of age will be studied to find when the ipsilateral-contralateral differences seen in neonates disappears. An on-line system for automated tonal audiometry utilizing the components of the off-line system will then be validated on actual clinical populations. Finally, recommendations for a practical, clinical implementation of the automated system will be promulgated.